In chemical industries, conversion of reaction solvents from organic solvents to water has been actively investigated for the purpose of cost reduction, safety, reduction of environmental loads and the like. However, there are only few examples of succeeding such conversion because of the problems of solubility of the reaction substrate or catalyst, safety and the like. In recent years, the inventors of the present invention succeeded in developing a Lewis acid catalyst which is stable even in water, and subsequently a Lewis acid catalyst integrated with a surfactant (see Patent Document 1), thereby greatly increased the possibility of carrying out synthesis reactions in water (see Non-Patent Document 1). Furthermore, the inventors of the present invention conducted investigation on the immobilization of a catalyst onto an insoluble support, for the purpose of facilitating the isolation of catalysts from products or the recovery/reuse of catalysts, and found that a Lewis acid catalyst which is bound to a hydrophobic polymer support and is stable in water, accelerates various reactions in water, compared with in an organic solvent (see Non-Patent Document 2, Patent Document 2 and Patent Document 3). Nevertheless, Lewis acid catalysts supported on organic polymers have problems such as that production of such catalysts is relatively difficult and expensive.
Meanwhile, in recent years, ionic liquids are attracting attention as a new reaction field (see Non-Patent Documents 3 and 4), and a biphasic reaction involving a solution or a gas has been recently developed, in which an ionic liquid is supported on the surface of a porous support so as to use the ionic liquid as an immobilized catalyst (see Non-patent Document 5). In addition, a method of performing a Heck reaction using a Pd/C catalyst in an ionic liquid (see Patent Document 4), a method of performing an aldol reaction using proline as a catalyst in the presence of an ionic liquid, and recovering and reusing the catalyst or solvent (see Patent Document 5), a method of using an ionic liquid as a catalyst in the isomerization of paraffinic hydrocarbons or in the production of high octane gasoline (see Patent Documents 6 and 7) and the like, have been reported. As such, ionic liquids are widely used as reaction solvents or catalysts. Furthermore, numerous improvements are also being added to the ionic liquids themselves, such as in the cases of an immobilized ionic liquid in which either the cations or the anions of the ionic liquid are immobilized (see Patent Document 8), a method for producing an ionic liquid from a Lewis acid having titanium, niobium, tantalum, tin or antimony as the base (see Patent Document 9), and the like. Also, a method of coating an enzyme with an ionic liquid and using the coated enzyme in an enzymatic reaction (see Patent Document 10), a method of using an ionic liquid as a liquid matrix in an organic reaction in a homogeneous phase (see Patent Document 11) and the like, have been reported.
However, examples of utilizing an ionic liquid phase as a hydrophobic field in reactions performed in aqueous solutions are yet to be known.
Patent Document 1: JP-A No. 11-244705
Patent Document 2: JP-A No. 2001-137710
Patent Document 3: JP-A No. 2005-254115
Patent Document 4: JP-A No. 2002-265394
Patent Document 5: JP-A No. 2002-275118
Patent Document 6: JP-A No. 2004-269846
Patent Document 7: JP-A No. 2005-314500
Patent Document 8: JP-W No. 2003-512926
Patent Document 9: JP-A No. 2003-535054
Patent Document 10: JP-A No. 2005-514033
Patent Document 11: JP-A No. 2006-500418
Non-Patent Document 1: Kobayashi, S., Eur. J. Org. Chem., 1999, 15.
Non-Patent Document 2: Iimura, S.; Manabe, K.; Kobayashi, S., Tetrahedron, 2004, 60, 7673.
Non-Patent Document 3: Welton T., et al., Chem. Reviews, 1999, 99, 2071-2083.
Non-Patent Document 4: Wasserscheid P, et al., Angewadte Chemie International Edition, 2000, 39(21), 3772-3787.
Non-Patent document 5: Gruttadauria, M.; Riela, S.; Aprile, C.; Meo, P. L.; D'Anna, F. and Noto, R., Adv. Synth. Catal., 2006, 348, 82.
Non-Patent Document 6: Jones, C. W.; Tsuji, K; Davis, M. E., Nature, 1998, 393, 52.
Non-Patent Document 7: Huddleston, J. G.; Visser, A. E.; Reichert, W. M.; Willauer, H. D.; Broker, G. A.; Rogers, R. D., Green Chem. 2001, 3, 156.